Update OpenNSA manifest to latest 6.5.21

Summary:
This is towards upgrading to newer OpenNSA 6.5.21.

This diff will be landed after we have verified that OpenNSA 6.5.21 has not
regressed from OpenNSA 6.5.19 (HW test results)

sha256sum on the tarball, and use that in the manifest.

Reviewed By: jasmeetbagga

Differential Revision: D27470306

fbshipit-source-id: a56c1e012a790b0bc948a5804dd605cdf224916c

Author: shri-khare

build/fbcode_builder/manifests/OpenNSA

@@ -2,12 +2,12 @@
 name = OpenNSA
 
 [download]
-url = https://docs.broadcom.com/docs-and-downloads/csg/opennsa-6.5.19.tgz
-sha256 = 80c3a26f688dd7fc08880fdbbad9ac3424b435697b0ccb889487f55f2bc425c4
+url = https://docs.broadcom.com/docs-and-downloads/csg/opennsa-6.5.21.tgz
+sha256 = f259519591981106ccad2842e89ab3c8515858ac784a5dbe0fa1513cb412421e
 
 [build]
 builder = nop
-subdir = opennsa-6.5.19
+subdir = opennsa-6.5.21
 
 [install.files]
 lib/x86-64 = lib